A majority of high elo players play around blitz very easily. Riot bases game balance off of High elo play and if those high elo found fault in blitz's kit and couldn't play against him then Riot would tweak the champion.
well high elo isn't always the best solution for every champ in this case blitz is a skillshot champ where he needs his grab low elo even gold have issues with blitz since its fast and small like teemo small and if you're dead center unless you have a dash or you got boots of swiftness first item chances are gonna get grabbed.
In return for having one of the best CC's in the game blitz sacrifices alot in return. High early mana costs, long CD's, a built in penalty to his chase ability, no good mobility besides his speedup which was heavily nerfed.
the two best cc in the game and one of the better ults but I'm about to get to that. high early costs there is a mastery to help that, and i always see blitz get mana crystals on first back so with items its hard to say high mana cost is a issue when its 100 40 and 25 with 100 for ult. the cds are not crazy 20 cd at level 1 for q isn't half bad unless you're just throwing hooks out, the built in penalty to his speed is new and doesn't stop him from positioning quickly if he's going for a grab in the lane or behind a wall he doesn't need to worry about the slow in fact the only way it's come up is when he's chasing or running away it becomes a issue. so items namely
as prime examples minigate his sacrifices so other than not landing his q what weaknesses does he have? how about a bolt that deals 100/200/300 damage when his passive is up or a ult that deals 250/375/ and 500 base damage with 100% scaling and silences that is up every 30 seconds or the fact that his grab will sometimes go longer than the tool tip shows or a knock up that deals double blitz ad. all of that on a squishy will usually mean death alone which beings me to..
Also a blitz pull does NOT = death, try playing a getting a tanky sup like leona or Naut and let them body block then when/if they get pulled it makes their job easier to engage.
unless blitz misses his q it will spell death for anyone but the tankiest of tanks in a team fight, in lane it will usually mean death if the enemy adc is paying attention and i would love to force the guy trying to get me kills to be leona or naut but then again i'm one of those "i don't know you're life be who you're best at" kinda adcs who wants this person who can make it a 2 v 2 or a 3 v 1 to feel good so they want to work together instead of "this guy is like every adc fine imma be leona or naut and feed" not really worth imo